156
FXUS63 KMQT 030735
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
335 AM EDT Mon Jun 3 2024

.KEY MESSAGES...

- Showers and a few thunderstorms progress eastward across west
  and central Upper MI today. Greatest coverage will be over
  the west. Severe storms not expected.
- Frequent opportunities for showers and thunderstorms over the
  next 7 days, with a break on Tuesday.
- Above normal temperatures through Wednesday, then turning
  cooler for the second half of the week.

&&

.SHORT TERM /THROUGH THIS AFTERNOON/...
Issued at 312 AM EDT Mon Jun 3 2024

Water vapor imagery and RAP analysis show weak mid-level troffing
over the Northern Plains. One vort max is noted over eastern ND, but
it`s difficult to pick out clearly any others. Radar imagery shows
shra/tsra from MN to Nebraska/KS with greatest coverage across MN
within 40-50kt low-level jet and the resulting 850mb theta-e
advection that has developed in response to the aforementioned ND
vort max. Radar imagery has occasionally been suggestive of
potentially one or two convectively induced weak vort maxes within
the shra/tsra area. The shra/tsra have spread out over nw WI, and
shra have recently arrived over far western Upper MI. Temps across
the fcst area currently range from the mid/upper 40s F at a few of
the traditional cold spots across the e to the mid 60s F at KIWD.

As shortwave over eastern ND lifts ene today, stronger core of the
low-level jet will mostly pass just nw and n of Upper MI, suggesting
that wider coverage of heavier rainfall will brush w and nw Upper MI
this morning. Meanwhile, with the southern end of the low-level jet
weakening to around 30kt at it translates over Upper MI today, would
anticipate a diminishing of shra as they progress across the area,
and much of the guidance indicates that. If a weak vort max is
concealed in the convection in MN, that would work to delay the
expected diminishing of shra. Of note is a better defined
convectively induced vort max over eastern Nebraska. Models indicate
that this feature will lift to Upper MI later this aftn, potentially
reinvigorating shra across the central and/or eastern fcst area.
Models have mixed signals on whether this feature will hold together
and/or aid shra. Will be something to monitor for an increase in
rainfall later aftn. Whatever the case, shra won`t reach the far
eastern fcst area until late in the day. CAPE is meager today with
abundant cloud cover limiting heating, but enough is present for non
sfc-based parcels or potentially sfc based parcels this aftn if
there is some thinning of clouds to maintain mostly just a schc
thunder mention. With expectation of clouds mostly dominating,
knocked high temps down a little. Expect upper 60s/lwr 70s F for the
most part, though eastern areas away from Lake MI should reach the
mid 70s due to thinner cloud cover thru at least the morning.

&&

.LONG TERM /TONIGHT THROUGH SUNDAY/...
Issued at 334 AM EDT Mon Jun 3 2024

As a cold front loses some steam over the eastern half of the U.P.
tonight, scattered shower and thunderstorm frequency lessens as they
continue to march eastward with time. With warm air advection from
the Gulf immediately moving in behind the front (one of the reasons
the cold front starts to die out), expect a saturated layer of air
up to 4 to 5 kft to bring some patchy fog and drizzle across the
U.P. behind the showers and thunderstorms of the dying front. This
will keep low temperatures tonight well above normal; temperatures
are projected to only get down into the mid 50s near Lake Michigan
to around 60.

Moving into Tuesday, expect skies to scatter out a little as the
last of the showers and storms moves out of the far eastern U.P.
into northern Ontario and the low-level clouds causing the
drizzle/patchy fog across the rest of the area scatters out during
the morning hours. CAMs have recently backed-off on precipitation
chances throughout the day Tuesday in comparison to the global
models. Therefore, while I`m thinking partly cloudy skies are still
likely (70+% chance) to occur across the area Tuesday, rainfall
chances shouldn`t enter into the U.P. again until late this
afternoon over the far west at the very earliest as a second,
stronger cold front approaches from the Northern Plains. With warm
air advection continuing ahead of the cold front, expect the warmest
temperatures of the week to occur Tuesday, with highs getting into
the 80s across some of the interior areas, particularly over the
west and downslope areas near Lake Superior where the increasing
southerly downslope winds throughout the day could locally increase
temperatures by at least a few degrees; the warmest temperatures
will likely be around Ontonagon to the Porkies. In addition to the
warm temperatures, Tuesday may also feel pretty muggy, with CAMs
bringing dewpoints into the mid to upper 60s by the afternoon hours.
Therefore, if you`ve got A.C., it may be your best friend on
Tuesday.

The cold front looks to begin bringing showers and thunderstorms to
the western U.P. Tuesday evening. Severe weather is currently not
expected with the passage of the cold front Tuesday night at this
time as the showers and storms associated with it are expected to
come during the overnight hours, when CAPE will be lacking in the
atmosphere. In addition, bulk shear values generally look to remain
well below 30 knots, which should prevent the updrafts from tilting
enough for the downdrafts of the storms to kill them. However, there
are some outlier models that, should they come together just right,
may allow for some strong to severe convection to reach the far
western U.P. Tuesday evening; this would bring some marginally
severe hail and winds to the far west before the convection
diminishes overnight. However, the chance of this occurring is very
low (<5%). With ensemble guidance showing PWATs above the 90th
percentile of climatology at around 1.5 inches, heavy rainfall seems
to be the main threat Tuesday night through Wednesday. I wouldn`t be
surprised if some places received over an inch of rainfall due to
the showers and storms via the abundance of moisture ahead of the
cold front. The cold front continues through the eastern half of the
U.P. Wednesday as a secondary shortwave drops down from Canada and
brings light rain showers and maybe a thunderstorm or two back
across the western half of the U.P. Wednesday afternoon behind the
front.

Behind the cold front, expect cooler temperatures to dominate the
rest of the extended forecast period as a synoptic troughing set-up
settles over Canada and rotates multiple shortwaves across our
region throughout the rest of this week and upcoming weekend. This
will bring multiple light rain shower chances across our area for
the rest of the extended period, and maybe a thunderstorm or two
during the afternoon hours when daytime heating becomes maximized.
In addition, I have a hunch that the dewpoints will be lower than
what the NBM is currently forecasting for the latter half of the
forecast period; with the cold air advection bringing dry northerly
air into our region, I wouldn`t be surprised if mixing in the
boundary layer is greater than what`s predicted by the medium range
models. Thus, there is a chance (~25-30%) that we could see min RHs
dropping down closer to 30% starting Thursday. However, my
confidence in this solution remains small at this time as there is a
bit of model divergence as to when exactly the shortwaves will
impact our area as model diffluence has increased between the
different medium range models on the shape of the upper-level
synoptic pattern. With the inclusion of rain showers increasing
dewpoints at the sfc throughout the latter half of the forecast
period from time-to-time, I decided to leave the dewpoints alone for
now. ECMWF EFI is also hinting at some windier conditions come
Thursday and Friday as the EFI values of 0.5 to 0.7 are expected
those two days. This may help to enhance drying at the surface and
increase wildfire spread (should any occur). The winds for Thursday
and Friday may need to monitored in future forecast packages given
the increased fire weather impacts they could have should the
gustier winds materialize.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 134 AM EDT Mon Jun 3 2024

VFR conditions should hold through mid to late morning when they
begin to deteriorate to MVFR starting with IWD.  An approaching
disturbance will spread rain showers into the area early this
morning, and cigs will eventually deteriorate as the environment
becomes saturated.  Best chances for any thunderstorms will be
confined to IWD where best forcing will be concentrated with strong
low-level jet.  Will, however, carry a LLWS mention at both IWD and
CMX this morning in association with said low-level jet.  At the
surface, southerly winds will also exceed the 12 kt threshold with
gusts up to 22 kts later this morning through this afternoon. And
for now, will lean toward a downward trend in cigs with IFR
conditions by Tue 03Z.

&&

.MARINE...
Issued at 334 AM EDT Mon Jun 3 2024

Southeast winds increase to 20 to 25 knots over the north-central
lake and the southerly shoreline today ahead of a cold front pushing
through; I wouldn`t be surprised if we had locally higher downslope
winds near the tip of the Keweenaw, given that it`s a `hotspot` for
stronger winds when the winds come from the southerly direction.
Once the dying cold front passes through, expect the winds to
slacken back down to 20 knots or less by this evening and to remain
that way until a second, stronger cold front moves through Tuesday
night and Wednesday, when southeast to southerly wind gusts of 20 to
25 knots will again be seen over the central lake and also probably
over the southerly downslope areas along the U.P.`s shoreline
(particularly the tip of the Keweenaw). Behind the cold front, we
could see southwest to westerly winds pick up to around 20 knots
over the west half of the lake Wednesday afternoon as a secondary
shortwave moves through. However, with model divergence increasing
and cold air advection decreasing for that point in time, gusts have
trended slightly lower than what was predicted yesterday. As
additional shortwaves rotate through our area the rest of this week
through this weekend, expect winds to increase from the west and
northwest at times; we could see westerly winds gust up to 20 to 30
knots Thursday and again to 20 to 25 knots from the northwest Friday
as shortwave lows impact the Upper Great Lakes.

As for other marine concerns this week, expect some patchy fog over
the western and north central lake today behind the cold front as
the moisture from the rainfall becomes trapped near the water`s
surface due to the strong temperature inversion caused by the cool
lake waters; the fog could be dense in some spots. This patchy fog
looks to persist until the second, stronger cold front moves through
Tuesday night and Wednesday, when the cooler air behind the front
could allow the moisture to mix out. As for the thunderstorm chances
this week, a few thunderstorms are expected to move from the far
western lake early this morning to the far eastern lake by Tuesday
morning. Thunderstorms return late Tuesday afternoon as the second
cold front moves into the far western lake; some severe weather
could be seen over the far west Tuesday afternoon and evening near
Duluth, although the chance for severe weather is still rather low
(~5%); severe hail and winds are the primary concerns. The
thunderstorm activity continues across Lake Superior from west to
east Wednesday until leaving into northern Ontario late in the day.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.

&&

$$

SHORT TERM...Rolfson
LONG TERM...TAP
AVIATION...TDUD
MARINE...TAP